svtplay-dl: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/svtplay-dl - from package: svtplay-dl

You may install the required package with command apt-get install {package}

Error in other languages:
svtplay-dl: bevel nie gevind nie
svtplay-dl: comandă negăsită
svtplay-dl: comando não encontrado
svtplay-dl: commande introuvable
svtplay-dl: command not found
svtplay-dl: käsku ei ole
svtplay-dl: không tìm thấy lệnh
svtplay-dl: komanda nerasta
svtplay-dl: Kommando nicht gefunden.
svtplay-dl: kommandot finns inte
svtplay-dl: komut yok
svtplay-dl: nie znaleziono polecenia
svtplay-dl: níor aimsíodh an t-ordú
svtplay-dl: no se encontró la orden
svtplay-dl: no s'ha trobat l'ordre
svtplay-dl: opdracht niet gevonden
svtplay-dl: parancs nem található
svtplay-dl: perintah tidak ditemukan
svtplay-dl: príkaz nenájdený
svtplay-dl: příkaz nenalezen
svtplay-dl: команда не найдена
svtplay-dl: командата не е открита
svtplay-dl: 命令找不到
svtplay-dl: コマンドが見つかりません